The main building block in a telecommunication network is a switching node, and a major factor that influences the shape of the network is the degree of each switching node. The nodal degree of a specific switching node is the number of adjacent nodes to which the specific node directly connects. As the nodal degree increases, the network diameter decreases rapidly; the network diameter being an indication of the number of intermediate nodes traversed by a path from a source edge node to a sink edge node. A decrease in network diameter decreases network complexity and improves network performance. A switching node of large dimension (hence large degree) can connect to a large number of adjacent nodes, hence reducing the diameter of the network.
Present switching nodes include time-division-multiplexed (TDM) switches developed for telephony services, data switches—such as Asynchronous-Transfer-Mode (ATM) switches—intended for networks planned to handle data segments of equal size, Internet-Protocol (IP) routers used to distribute packets of variable size, and coarse TDM cross-connectors such as SONET (Synchronous Optical Network) nodes and SDH (Synchronous Digital Hierarchy) nodes used for managing the capacity of optical links interconnecting switching nodes.
New network services having diverse flow rates, varying, for example, from 1 kilobit per second to 100 megabits per second, would naturally call for a scalable multi-granular edge node capable of efficiently switching data of distinctly different granularities and interfacing with core nodes of different types. An envisaged multi-grained high-capacity network may include legacy IP core routers in addition to optical time-shared core switches such as optical TDM switches and optical burst switches for switching bursts of relatively long duration. There is a need, therefore, to develop multi-grained edge nodes capable of interfacing with a variety of core switches operating at distinctly different granularities.